It't me wrote:
Hi all,
I'm learning Python with Google's Python class
Ik have a question about the following code:
=================================
def sort(var):
return var[-1] #returns the last character of var
Why is the function called "sort" when it doesn't sort?
Why not call it "run" or "cook" or "pink" or "xhg6gf2jgf"?
Function names *must* tell you what they do, or at least give you a
hint. Misleading names like "sort" for something that doesn't sort is
very bad. Even a name like "xhg6gf2jgf" would be better than a name that
lies about what it does.
def sort_last():
tup = [(1, 3), (3, 2), (2, 1)]
print(sorted(tup, key=sort))
sort_last()
==================================
I uderstand everything except (var) value.
I understand that key=sort calls the sort function.
Do you mean the sort function you wrote, or the built-in list sort
method? I'll assume you mean the sort function you wrote.
But where comes the var value from?
Does sort automatic pass the value from tup to (var)
No. sorted() passes the values to the key function "sort". "sort"
*receives* those values, it doesn't go and get them.
When you write a function with an argument, the argument isn't defined
until you call it:
def add_one(x):
return x + 1
x is a local variable of the function, but is not yet defined. But when
you call the function:
add_one(42)
x is set to 42.
In your "sort" function, the local variable is called "var". Calling
sorted(tup, key=sort)
with tup = [(1, 3), (3, 2), (2, 1)] results in the sorted() function
calling your key function "sort" with each of the items in turn:
* build a new list by calling the "sort" function with (1,3), then
(3,2), then (2, 1)
* sort a copy of the original list according to the values in the new list
* return the sorted copy
--
Steven
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